Coated hemi-prosthesis implant

ABSTRACT

A hemi-prosthesis implant comprises a replacement-joint part with an articulation surface for tribological pairing with a joint surface of a natural joint counterpart. The articulation surface is embodied with a coating applied on a substrate. The substrate provides a relief for the adhesion of the coating. The relief may comprise one or more of a plurality of grooves, a plurality of teeth, a ribbing, and a roughened surface. The relief may be embodied entirely or partially outside the articulation surface. The replacement joint part may optionally comprise a ventilation feature, and the articulation surface may be formed by injection molding on the substrate. The hemi-prosthesis implant may be part of an implant set that includes both a hemi-prosthesis implant and a total prosthesis implant, either of which can be chosen intraoperatively.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(a)-(b) and 35U.S.C. § 365(a)-(b) to International Patent Application No.PCT/EP2014/074865 (published as WO 2015/096938 A1), which was filed onNov. 18, 2014, and to German Patent Application No. 10 2013 227 136.0,which was filed on Dec. 23, 2013. Both of those applications are herebyincorporated by reference herein in their entireties.

TECHNICAL FIELD

This disclosure relates to a hemi-prosthesis implant, an implant setcomprising a hemi-prosthesis implant, and a method for the manufactureof a hemi-prosthesis implant.

BACKGROUND

Implants are artificial, that is, non-natural, structures that areimplanted into a human or animal body, for example, in order to replacea joint entirely or partially in the form of an endoprosthesis. Theaffected joints can be, for example, a shoulder, hip, knee, or anklejoint.

A joint comprises two bone ends, that is, joint halves, which face oneanother in a movable manner with the respective joint or tribologicalfaces. In the case of ball joints, such as the shoulder joint or hipjoint, one joint part has a concave tribological face, for example theglenoid in the shoulder joint or the acetabulum in the hip joint, whilethe other tribological face of the tribological pairing, for example,the humerus head or upper-arm head in the case of the shoulder joint, orthe femur head or thigh-bone head in the case of the hip joint, isembodied in a convex manner.

With regard to a joint replacement, there is a distinction between atotal prosthesis and a hemi-prosthesis. A total prosthesis replaces theentire joint; that is, each of the two joint halves is replaced by animplant, wherein the implant is anchored in the remaining bone. Thetribological pairing between the convex and concave replacement-jointparts is mediated exclusively by artificial materials.

A hemi-prosthesis replaces only one joint half, generally the convextribological partner. By comparison with a total prosthesis, theintervention is less serious and the stress on the patient is reduced. Ahemi-prosthesis can be selected, for example, if the cartilage of thenatural, concave tribological face of the glenoid, acetabulum, or tibialplateau in the knee, etc. is healthy and intact. For example, in thecase of the hip joint, with a damaged femur head or fractured neck ofthe femur, both parts of the femur bone are replaced, but, with regardto the pelvis side, the acetabulum is retained.

Replacement joint parts must be sufficiently strong to transfer theforces acting on the joints in the long-term. Accordingly, implants inthis region are often manufactured from metal or ceramic. However, inthe case of hemi-prostheses there is the problem that strong prosthesismaterials are not good frictional partners for the natural cartilage ofthe other joint half. Accordingly, it is known that, for example, steelor cobalt alloys cause damage which can go as far as destroying thecartilage.

Various materials which can be used as tribological partners for thecartilage instead of metal or ceramic have been suggested. So far,results relating to their actual suitability are available only for afew of these materials. However, the materials can be categorized bycomparison with metal or ceramic roughly into rigid or hard, on onehand, or less rigid or less hard materials. Examples of hard materialsinclude, for example, oxide-ceramic coated metals, such as oxidizedzirconium, oxidized ceramic, pyrolytic carbon (pyrocarbon).

Examples of materials tending to be less rigid include various syntheticmaterials. At least some of these materials are not strong enough to beused as base materials for the manufacture of implants such asreplacement joint parts. A corresponding implant must therefore be builtup in two parts, that is, it must comprise a strong material with acoating made from a cartilage-sparing material. However, how a rigidsubstrate material can be joined permanently and inseparably with a lessrigid coating material with regard to the forces acting in a jointremains problematic.

It is known from EP 2 086 471 B1 that a pyrocarbon shell can be fixedonto a metallic carrier. In this context, a polyethylene intermediatelayer is provided. The pyrocarbon shell is embodied with a bottom edgedirected inwards, which engages in a corresponding peripheral recess ofthe polyethylene intermediate layer, thereby providing a compressionfit. The polyethylene casing and the metallic carrier each provides acorresponding peripheral groove in which an annular holding ring isretained. This arrangement can be suitable for the attachment of rigidmaterials such as pyrocarbon but cannot be transferred to other, lessrigid materials.

SUMMARY OF THE DISCLOSURE

According to one embodiment, a hemi-prosthesis implant comprises areplacement joint part with an articulation surface for tribologicalpairing with a joint face of a natural joint counterpart. Thearticulation surface comprises a coating applied to the substrate. Thesubstrate provides a relief for the adhesion of the coating.

In some embodiments, the implant comprises the replacement joint part asa single component. This can be, for example, a one-piece prosthesisshaft embodied, for example, as a mono block, with a replacement head.In the case of other embodiments, the implant comprises one or morefurther components alongside the replacement joint part. For example, animplant can comprise, as the replacement joint part, a replacement headand a prosthesis shaft as further, separate components.

The articulation surface of the replacement joint part can be embodiedat least in regions as convex, in order to articulate with a concavejoint surface of a natural joint part or joint counterpart.

The implant, that is, the replacement joint part and/or furthercomponents, can comprise, for example, a humerus head hemi-prosthesis, afemur-head hemi-prosthesis, a femur hemi-prosthesis component, forexample, a condylar joint replacement and/or meniscus replacement or atalar body hemi-prosthesis.

The substrate for the coating can be formed from a material of the baseelement of the replacement joint part. If the replacement joint partcomprises substantially, for example, a material such as a metal orceramic, with regard to load-bearing and/or force transmission, thismaterial can form the substrate. In some embodiments, at least one ofthe following materials is used for the manufacture of the substrate: ametal, such as titanium; one or more titanium alloys; steel, especiallystainless steel; one or more cobalt alloys; zirconium; one or morezirconium alloys; tantalum, one or more tantalum alloys; one or moremolybdenum alloys; a ceramic, for example, an aluminium-oxide ceramic;zirconium-oxide ceramic; one or more mixed ceramics, such asaluminium-oxide zirconium oxide; or a synthetic material, for example, areinforced synthetic material, such as a fiber-reinforced syntheticmaterial.

The substrate can also be formed entirely or partially from a differentmaterial from that of the base element, for example, the material of anintermediate layer formed on a base element can form the substrate. Thematerial of the intermediate layer can also be, for example, a rigidmaterial, for example, one of the materials named above and/or anothermaterial, such as pyrocarbon. Additionally or alternatively, thematerial of the intermediate layer can also be a different syntheticmaterial, such as polyethylene, for example, if an intermediate layercomprises several sub-layers.

With regard to its property as a substrate layer for a coating, thesubstrate can also be referred to by the following terms: base layer,foundation, under-layer, carrier, or base.

By comparison with other dimensions of the replacement joint part, thecoating can form a thin layer on the substrate. The thickness of thecoating can be, for example, less than 20%, or less than 10%, or lessthan 5% of a radius of a convex replacement-joint part. Accordingly,under some circumstances, the coating can also be regarded as a cap, acoat, a covering on the substrate, a skin, a casing, a cladding and/or ashell.

The coating can comprise one material or several materials from thefollowing list: a thermoplastic elastomer (TPE), polycarbonate urethane(PCU), a polyolefin polymer, a UHMWPE (ultra-high molecular weightpolyethylene), an XUHMWPE (cross-linked UHMWPE), a UHMWPE or XUHMWPEwith one or more additives, such as vitamin E, a polyaryl ketone orrespectively polyaryl ether ketone, a polyether-ketone ketone (PEKK), ahydrogel based on PVA and/or PVD.

The substrate under the coating can be structured or contoured, forexample, so that the substrate provides the relief for the adhesion ofthe coating. Reference could also be made to a terrain or a topographyof the substrate instead of a relief. The relief offers a structure forthe engagement, the adhesion, or the holding for the coating. Anyenlargement of the surface area of the substrate in order to achieve astable anchoring, for example, of an injected coating or respectivelycap, can be understood in the present context as a relief.

The relief can provide a structure which is lowered or recessed bycomparison with a base surface. For example, the relief can compriserecesses or indentations. A depth of such recesses can be approximatelycomparable to or smaller than a thickness of the coating. For example, amaximum depth of the recesses of a relief can be 100% or less of acoating thickness, or 50% or less, or 30% or less, or 10% or less.

A recess or indentation in the relief can be embodied locally orpunctually, for example, in the form of a groove or concavity, undercut,etc. With some embodiments, punctual indentations can be arrangedaccording to global or large-area patterns on the articulation surface.For example, punctual indentations can be arranged in a linear manner,that is, along lines, and/or over an area forming regions with aplurality of indentations.

Additionally or alternatively, linear recesses can be formed, forexample, in the form of a plurality of grooves, striations, channels,furrows or slots, optionally with undercuts. The recesses can extendlocally in a rectilinear manner, wherein in the case of convexarticulation surfaces, for example, large circles can be obtained arounda head region of the replacement-joint part. Other recesses can providea local curvature and can describe, for example, partial or completecircles, wavy lines etc.

Additionally or alternatively, two-dimensional recesses can be formed.For example, a plurality of recessed regions can be present. Forexample, rectangular, square, circular and/or half-moon shaped recessedregions can be present.

With many embodiments, the relief can provide at least two mutuallycrossing grooves. Crossing angles between crossing grooves can be acute,that is, can be 45° or less, and/or can be obtuse, that is, greater than45°. In different embodiments, the relief comprises a plurality oflongitudinal and transverse grooves, wherein, in each case, alongitudinal groove and a transverse groove cross at an angle of 80° ormore.

As a result of regularly crossing grooves, for example, grooves and/orother types of linear indentations arranged in a mesh, a plurality ofraised regions can be defined, which can be, for example, approximatelysquare, rectangular, diamond-shaped or otherwise segment-shaped. In thismanner, for example, a ribbing of the substrate can be embodied.

With given embodiments, the relief comprises one or more roughenedsubstrate regions. A roughening can introduce an irregular pattern intothe substrate. A roughening can be present in multiple regions, forexample, a plurality of uniformly roughened regions can be present in achessboard pattern, or along a large circle, etc. The roughness can becorrespondingly pronounced, as described above for the depth ofrecesses.

In addition to or as an alternative to indentations or roughening, therelief can provide a structure which is raised or prominent bycomparison with a base surface. It should be noted, that, for example,in the case of multiply structured reliefs, the definition of a basesurface and therefore the definition of a structure as an indentation ora raised area can be arbitrary.

Raised regions or projections in the relief can be formed locally orpunctually. For example, the relief can provide a plurality of peaks,humps, teeth, spikes, barbs, crenulations, bumps, etc. With someembodiments, punctual raised areas can be arranged according to globalor large-area patterns, for example, in a linear or two-dimensionalmanner forming corresponding regions with a plurality of raised areas.

Additionally or alternatively, raised areas can be embodied in a linearmanner, for example, in the form of local projections, overhangs, edgesetc. extending in a rectilinear or curved manner. Additionally oralternatively, raised areas can be embodied in a two-dimensional manner.For example, rectangular, square, circular and/or half-moon shapedraised areas can be present.

Some embodiments of the relief comprise a plurality of raised areasarranged in a linear manner, thereby forming a plurality of rows ofteeth on the substrate surface. A row of teeth can be formed, forexample, by teeth, crenulations or barbs, which project above a basesurface or a raised edge or other linear projection, thereby formingteeth, a knurling or notching.

In some of these embodiments, the relief provides a plurality of rows ofteeth extending longitudinally; for example, such rows of teeth canextend, in the case of a spherical-segment-shaped or otherwise roundedconvex articulation surface, in the direction from a top to a basedisposed opposite to the top of the replacement joint head or otherlimit of the articulation surface. Additionally or alternatively,transversely extending rows of teeth can be provided, and the rows ofteeth can extend in a zigzag shape, which cross over one another, whichform an X-shape etc.

With some embodiments, at least one ventilation borehole leading intothe substrate can be provided. For the ventilation boreholes, it issufficient that they allow a passage or a penetration or escape of airor of another atmosphere which is present, for example, during theapplication of the coating. This can apply in general or in regions inwhich a lateral escape into given regions is hindered, that is, forexample, in indentations, for example, in a groove. The ventilationboreholes should not be so large that they significantly reduce anadhesion surface of the substrate and/or allow a passage of an appliedcoating, for example, an injection molding material, into the internalregion of the base body.

Boreholes can be introduced punctually, that is, for example, ascylindrical boreholes, or can be introduced with a preferredlongitudinal extension, that is, for example, as a slot or groove. Anelongated ventilation gap can extend, for example, along a groove, forexample, at the bottom of a groove. Such a gap could substantiallyprovide the length of the groove, or a plurality of ventilation gaps ofshorter length can be introduced along the groove; additionally oralternatively, a ventilation gap can be subdivided by bridges or ribs. Aplurality of circular boreholes can also be introduced along the bottomof a groove, so that the bottom of the groove is pointed at regularintervals.

Boreholes can extend into the base body. Ventilation boreholes caneither terminate as blind boreholes or can be open, that is, penetratecompletely through the base body, for example, by extending into acentral or internal recess of the base body. Ventilation boreholes witha blind termination can extend so far until the desired ventilationeffect can be achieved. Hybrid forms are conceivable, for example, aventilation groove or gap can be provided with punctual, open boreholes,which open into a closed or open hollow cavity of the base body.

Additionally or alternatively to the ventilation boreholes, ventilationgrooves which extend along the substrate can be provided. As in the caseof the ventilation boreholes, it also applies for the ventilationgrooves that these should be small relative to their depth, width and/orlength, and, in fact, by comparison with the actual adhesion structures,such as the anchoring grooves, in order not to influence an anchoringeffect, that is, an adhesion of the coating, in an undesirable manner.

Ventilation boreholes and/or grooves can be provided independently ofrelief structures, that is, ventilation boreholes or grooves can beprovided in a substrate region of the base body of the prosthesis inwhich no relief is provided. Additionally or alternatively, ventilationboreholes or grooves can be aligned with relief structures such asindentations or raised structures. Accordingly, for example, ventilationgrooves can be provided along an indentation, for example, ventilationgrooves can lead into or respectively lead away from such indentations.However, ventilation boreholes or grooves can also be provided adjacentto projections, such as teeth.

For example, a network or pattern of individual and/or crossingventilation grooves can be provided. For example, a pattern ofventilation boreholes and/or grooves can be provided in combination witha roughened substrate region. Alternatively or additionally, a patternof ventilation boreholes and/or grooves can be provided in conjunctionwith a flat substrate region. Exemplary embodiments of hemi-prosthesisheads are also conceivable, which provide no relief, but which doprovide ventilation boreholes and/or grooves. For example, a network orpattern of ventilation boreholes and/or grooves can extend over a partof the substrate or over the entire substrate which is covered by thecoating; that is, the pattern can extend below and/or outside thearticulation surface.

Whether ventilation boreholes and/or grooves are provided and how theseare set out, can depend in individual cases upon the coating materialused, upon structures of the substrate, such as the number andarrangement of grooves, teeth, etc. The purpose of use can also be takeninto consideration, for example, whether a large or a small jointreplacement is involved. The required anchoring effect may also bespecified by a desired load-bearing capacity. Optionally, experimentsmay be implemented regarding which ventilation structures lead to anoptimal adhesion of the coating on the substrate or respectively on thecap of the base body.

A base body which forms the substrate can provide a pedestal exposed tothe exterior. With some embodiments, an at least partially peripheralanchoring groove can be embodied directly on the pedestal, which serves,for example, to anchor the casing or respectively the cap on the basebody. With these or with other embodiments, an exposed pedestal regionof the base body forming the substrate can be embodied with a sharp edgeat the transition to the articulation surface, for example, in order tominimize a joint gap at the outer or exposed limit between the cap andthe base body.

The substrate on which a relief, a ventilation borehole, etc. can beembodied comprises the entire substrate on which a coating, cap, etc.can be or is embodied. Accordingly, the substrate can comprise a surfaceof the prosthesis base body which is disposed below the articulationsurface but can also comprise surface regions of the base body which arenot disposed below the articulation surface but alongside or outside it.The formulation used here that a relief might be disposed “outside” thearticulation surface is understood to mean that the surface of thecoating or cap disposed above a relief is not, or at least not duringnormal joint movements, disposed in contact with a joint counterpart(for example, cartilage) but is in contact, for example, with the boneor surrounding tissue surrounding a prosthesis shaft. In general, thecoating or cap provides a surface which is larger or includes more thanthe articulation surface; this means that, in general, the substrate isalso larger than the (normal) articulation surface.

With some embodiments, a relief is embodied only on the substrate or onsubstrate regions below the articulation surface. With otherembodiments, the relief extends over a substrate region which is notdisposed under the articulation surface. For example, substrate regionscan provide a relief or several reliefs below and alongside thearticulation surface. In many of these embodiments, the relief can bedisposed alongside the articulation surface to a substantial extent.

For example, in the case of a base body embodied in a substantiallyspherical shape, the relief can leave a substrate region at the topfree, that is to say, there is no relief under a central region of thearticulation surface. With another example, a region above an equatorcan be left free, that is, there is no relief in a region which does notbelong to the articulation zone in normal movement processes.

With some embodiments, no relief is present below the articulationsurface, that is, the substrate provided by the prosthesis body is flatthere, and a relief is disposed exclusively outside the (normal)articulation zone, that is, outside the zone which is articulateddirectly against the (natural) joint counterpart, such as cartilage,during the normal movement range of the joint. For example, in the caseof a femur head, this would be the zone below the equator, that is, inthe direction towards the prosthesis shaft; for example, in the case ofa humerus head, this would be the flat face pointing towards theresected humerus.

How large the area is and/or in which region a relief is applied, candepend, for example, upon the adhesive effect to be achieved. Below thearticulation surface, for example, a relief can be omitted completely orin part if the anchoring of the cap achievable with the remaining reliefis adequate. In the case of embodiments in which a relief below thearticulation surface is omitted in its entirety or partially, a reliefmay comprise only a pedestal region of the base body, a region such asan edge or groove in which the cap is to engage, etc.

In one approach, an adequate adhesive effect can be achieved with aventilation by means of corresponding ventilation boreholes and/orgrooves, so that a relief does not extend over the entire substratebeneath and/or outside an articulation zone. In this context,ventilation boreholes and/or grooves can be provided either in theregion of the articulation zone, even if no relief is present there,and/or ventilation boreholes and/or grooves can be provided in regionsoutside the articulation zone, for example, in a region where the reliefis present, that is, together with the relief, and/or in a region whereno relief is present.

Some of the embodiments mentioned offer options for minimizing adeviation of the substrate from a target geometry in the region of thearticulation surface. Dispensing with a relief below the articulationsurface entirely or partially can be advantageous, for example,dependent upon a material used for the coating, if, injection faults,such as sinking points, the occurrence of which could lead to deviationsfrom the target geometry of the articulation surface, can be avoided inthis manner.

A deviation from a target geometry may also be required, for example,for safety reasons, for example, in view of legal provisions or at therequest of a medical supervisory authority, for example, for any jointreplacement or for a joint replacement with particularly heavy loading,for example, in the hip or knee region. The requirement may be that thebase body presents no rough or rasp-like surface, also in the event ofan accident, overloading, etc. and/or a potentially occurring failure ofthe coating, but provides a smooth face as an auxiliary articulationsurface.

According to one embodiment, a hemi-prosthesis implant comprises areplacement joint part with an articulation surface for tribologicalpairing with a joint face of a natural joint counterpart, wherein thearticulation surface is embodied with a coating applied to a substrateand at least one ventilation feature leading into or extending in thesubstrate is provided. The ventilation feature may be, for example, aborehole or groove, either of which can be embodied in a region of thesubstrate below the articulation surface. Additionally or alternatively,a ventilation feature can be embodied in a region of the substrateoutside the articulation surface. With regard to embodiments of suchhemi-prosthesis implants without a relief but with ventilation features,the present descriptions of example embodiments with relief and withventilation feature(s) shall apply by analogy where applicable.

Furthermore, according to one embodiment, an implant group or implantset is proposed. The implant set comprises an implant base for holding areplacement joint part. The set further comprises a total prosthesisimplant with a first replacement joint part and a second replacementjoint part. Both replacement-joint parts provide, respectively, anarticulation surface for tribological pairing with the otherarticulation surface. The set further comprises a hemi-prosthesisimplant with a third replacement joint part as outlined above ordescribed elsewhere in the present document. The first and also thethird replacement joint part are provided for holding on the implantbase.

The implant set can provide a modular implant system, by means of whichit is possible to decide, for example, intraoperatively, whether a totalprosthesis or a hemi-prosthesis should be implanted. For a totalprosthesis, the first replacement joint part should be mounted oranchored on the implant base; for a hemi-prosthesis, the thirdreplacement joint part should be mounted on the implant base.

The implant base can comprise, for example, a prosthesis shaft and/oranother anchoring in a bone. Additionally, the implant base can providea mounting possibility for the mounting of the first and/or thirdreplacement joint part. One and the same mounting possibility can beprovided for the alternative mounting either of the first or of thethird replacement joint part. The mounting can be provided, for example,for plug-connection, for twist-connection, or for screw-connection ofthe first or third replacement joint part in the implant base.

Furthermore, a method for the manufacture of a hemi-prosthesis implantis proposed herein. The method comprises the provision of a relief on asubstrate of a replacement joint part for the adhesion of a coating. Afurther step comprises the application of the coating for the embodimentof an articulation surface of the replacement joint part fortribological pairing with a joint surface of the natural jointcounterpart.

During the manufacture of the replacement-joint part, the relief can beintroduced into the substrate, for example, during the processing of amaterial. Additionally or alternatively, a replacement joint part can bemanufactured without relief, and a relief can be introduced in adownstream step.

For the introduction of the relief, per se known techniques for metalprocessing can be used, if the replacement joint part provides a coatingsubstrate made from metal, a metal alloy, etc. For example, aretrospective introduction of relief structures such as grooves can beimplemented by milling. The introduction of a roughening can beimplemented by means of blasting methods and/or in a chemical manner. Ifthe coating substrate comprises a ceramic, a relief can preferably beintroduced already during the manufacture of the replacement joint part,for example, during a casting process, by modelling, etc.

For the embodiment of the coating, a material such as a TPE can beapplied to the substrate provided with a relief, for example, in aninjection molding process. The material can be present, for example,initially in a pourable form, in order to fill up the relief, that is,for example, to flow around raised portions or to flow intoindentations. After this, the material can harden and, in this manner,can embody the coating, for example, in the form of a cap or a casing onthe base body of the replacement joint part. With some embodiments, abase body on which the substrate is embodied, can be used as an insertin an injection molding process.

Additionally or alternatively to injection molding processes, othermethods can be used. For example, coating material can be sprayed orsintered onto the substrate, the replacement joint part can be immersedin a bath with coating material, etc. A cap or a casing or similarstructure can also initially be manufactured separately for the coatingand can then be attached to the substrate, for example, by means ofclamping, fixing, gluing, etc.

According to different embodiments, an implant for hemi-prostheses isprovided, in which a base body is formed from a rigid material. The basebody made from rigid material can mediate a force transmission such ascan occur in a joint. The base body can provide a substrate, onto whicha less rigid material is applied in order to form an articulationsurface, which can have a better biocompatibility than the rigidmaterial of the base body. This configuration offers the possibility touse as the coating material a material which is in fact less strong butmore compatible than the material of the rigid base body. Abiocompatibility may comprise, for example, tribological propertiesand/or a biological compatibility with tissue, such as cartilage,occurring naturally in the body of a human or animal. Thebiocompatibility can have the effect that a cartilage of a joint surfaceof a natural joint is preserved longer and/or provides an increaseddegree of health, intactness, etc. than if the articulation surface wereto be formed by the material of the base body.

With different embodiments, the material forming the articulationsurface can be applied to the base body as a coating. The coating shouldbe attached as securely and permanently as possible to the base bodywhich bears the load. For this purpose, a relief is provided on thecoating substrate, which serves for an improved adhesion of the coatingon the substrate, and, in fact, by comparison with an adhesion on asubstrate without relief.

The relief can form an engagement structure, a gripping structure, or aholding structure which is especially optimized for the adhesion of acomparatively less rigid material, for example, which cannot be attachedor cannot be attached reliably and/or cannot be attached adequately by acompression seating or snug-fit. Relief structures should offer anoverall holding, for example, to a cap formed by the coating, so thatthe latter is permanently secured against displacement or slipping.However, in this context, engaging excessively strongly in the lessrigid coating material should be avoided in order to prevent localdamage.

With a sufficiently hard material, a single nail, pin or tooth, or anindividual peripheral edge, groove or fitting, for example, could beadequate to achieve an attachment. According to embodiments of theinvention, two-dimensional holding structures can be provided in thecase of less hard or rigid material, which, however, avoid a localover-stressing of the material in order to minimize the risk of tearing,piercing, crack formation, etc. in the long-term and, in this manner, toachieve a permanent long-term and secure fitting of the coating withoutloosening over the course of time.

According to some embodiments, the occurrence of mechanical stresses inthe coating, which can occur in the case of a differently pronouncedadhesion of the coating on the substrate, can be minimized. According todifferent embodiments, reliefs covering the articulation surface canrealize different balances between two-dimensional covering with reliefstructures such as teeth or grooves, on the one hand, and the localstressing of the coating by these structures. Accordingly, a permanentand secure fitting of the coating on the base body can be optimized fordifferent coating materials, base-body materials, replacement jointtypes, purposes of use of the prosthesis for sports people, olderpeople, etc.

The risk of a slipping or displacement of the coating or respectivelycap occurring in the long-term and/or during given joint movements canbe minimized through appropriate embodiments of reliefs, which offer,for example, a hold against forces occurring tangentially to thesubstrate, independently of the directions in which these forces act.For example, a relief can minimize the danger of slipping tangentiallyrelative to the substrate in the longitudinal direction and/or in thetransverse direction.

According to some embodiments, a relief can be formed by structures suchas teeth and/or grooves, wherein an individual structure is embodied insuch a manner that, by comparison with the overall relief, it absorbs asmall force, that is, that a single such structure cannot prevent amovement of the cap. For example, a few teeth, which are, however,formed in a pronounced manner, can be embodied in the case of arelatively hard material, while more teeth can be embodied in the caseof a softer material, which can, however, be less pronounced.Corresponding conditions can apply for embodiments of reliefs withroughening, ribbing, etc.

With some embodiments, a secure and permanent holding of the coating capon the base body can be achieved at low cost. For example, a singlecoating on the base body can be sufficient so that no further layers,such as one or more intermediate layers, are required. It is sufficientto embody an appropriate relief in the coating substrate provided by thebase material. This relief can be manufactured through techniques, forexample, of material processing, which are per se known and can be usedcost effectively. For example, known injection molding techniques can beused for the coating.

Embodiments described herein extend the possible applications forhemi-prostheses, for example, by providing hemi-prostheses with improvedcompatibility which are reliable in the long-term. Hemi-prostheses withbiocompatible coating can also be used, for example, even in the case ofa heavy or enduring stress on the joint, because the coating adherespermanently and reliably to the base body even under heavy stress.

In view of the possibilities for cost-favorable manufacture and/or thepossibility for long-term retention in the body, for example, withoutcartilage damage necessitating a total prosthesis after a comparativelyshort time, the hemi-prostheses described herein can be used more widelyas a cost-favorable alternative to the total prosthesis in spite of theoptional additional coating. In this context, operation times are alsoshorter and, in general, the stresses on the patient are reduced.Accordingly, it should be taken into consideration that, if anysubsequent treatment of the remaining natural joint half were still tobe required, this would be a comparatively simpler initial implant andnot a revision.

According to some embodiments, an implant set is provided in which amodular total joint replacement system with an implant base in the boneand joint replacement for connection with the implant base can besupplemented by a hemi-prosthesis implant which comprises a furtherjoint replacement. For example, a modular replacement joint implantsystem can comprise a set of convex replacement joint parts (forexample, femur head, humerus head or femoral condyles of the knee) madefrom metal or ceramic in various sizes for the total replacement,wherein, in each case, a corresponding convex replacement-joint partwith improved biocompatibility is also available as a hemi-prosthesisfor every size. In this manner, a surgeon can decide in a flexiblemanner, even intraoperatively, for a total replacement or partialreplacement, which brings advantages for the patient, with regard totreatment costs etc.

BRIEF DESCRIPTIONS OF THE DRAWINGS

In the following, further aspects and advantages of the embodiments aredescribed by way with reference to the following attached drawings.

FIG. 1 illustrates, in schematic form, a modular implant set for areplacement hip joint according to a first example embodiment of theinvention.

FIG. 2 illustrates in schematic, semi-transparent form, details of thefemur head hemi-prosthesis from FIG. 1.

FIG. 3 illustrates in schematic form, a modular implant set for areplacement shoulder joint according to a second example embodiment ofthe invention.

FIG. 4 illustrates in schematic, semi-transparent form, details of thehumerus head hemi-prosthesis from FIG. 3.

FIG. 5 illustrates in schematic, semi-transparent form, details of afemur hemi-prosthesis component according to a third example embodimentof the invention

FIG. 6A illustrates in plan view, a relief according to a fourth exampleembodiment of the invention.

FIG. 6B illustrates in plan view, a relief according to a fifth exampleembodiment of the invention.

FIG. 6C illustrates in profile view, a relief according to a sixthexample embodiment of the invention.

FIG. 7A illustrates a prosthesis base body of a seventh exampleembodiment of the invention.

FIG. 7B illustrates a detailed view of the base body according to FIG.7A with a ventilation borehole and ventilation groove.

FIG. 7C illustrates a detailed view of the base body of FIG. 7A with ananchoring groove.

FIG. 8 illustrates a prosthesis head with base body and coating of aneighth example embodiment of the invention.

FIG. 9 illustrates in the form of a flow diagram, the course of a methodfor the manufacture of a hemi-prosthesis implant according to oneembodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

With reference to the above-listed drawings, this section describesparticular embodiments and their detailed construction and operation.The embodiments described herein are merely examples, set forth by wayof illustration only and not limitation. Those skilled in the art willrecognize in light of the teachings herein that there are alternatives,variations and equivalents to the example embodiments described herein.For example, other embodiments are readily possible, variations can bemade to the embodiments described herein, and there may be equivalentsto the components, parts, or steps that make up the describedembodiments.

As one skilled in the art will appreciate in light of this disclosure,certain embodiments may be capable of achieving certain advantages,including, in some cases, providing a hemi-prosthesis in which animplant is built up from a rigid base material, but an articulationsurface is formed from a less rigid material, and in which a permanentand secure joining of the less rigid material to the base material isoptimized, with regard to considerations inter alia of cost.

FIG. 1 shows in schematic form components of an implant set 100 for areplacement hip joint. The implant set 100 comprises an implant base,namely, a femoral shaft 102, and a convex total prosthesis part as atotal prosthesis implant, namely, a total prosthesis head 104 and aconcave total prosthesis part, namely a total prosthesis socket 106, anda convex hemi-prosthesis part as a hemi-prosthesis implant, namely ahemi-prosthesis head 108. The implant set 100 can comprise more than thecomponents shown. For example, implant base, prosthesis heads and/orprosthesis sockets can be provided in different sizes; heads and/orsockets can be made from different material and/or with differentcoatings etc.

The hip shaft or femur shaft 102 is provided with an anchor portion 110for anchoring in a femur bone. With the implantation of a totalprosthesis, at the one end, a femoral joint head is replaced by thetotal prosthesis head 104 as a replacement joint part (in conjunctionwith the implant base 102); at the other end, an acetabulum is replacedby the total prosthesis socket 106 as the replacement joint part. Forthe implantation of a hemi-prosthesis, only the femoral joint head isreplaced by the hemi-prosthesis head 108 (in conjunction with theimplant base 102).

The implant base, that is, the femur shaft 102 can be made, for example,from a non-rusting steel, stainless steel, a metal alloy, etc. For themounting of precisely one of the prosthesis heads 104 or 108, the femurshaft 102 comprises a mounting portion 112, which, in the example,comprises a plug-in shaft for the plug-in attachment of one of the heads104 or 108. Each of the heads 104 and 108 provides a correspondingcoupling 114 or 116 respectively. In the example, each coupling 114, 116comprises a recess for a plug-in connection with the plug-in shaft 112of the implant base 102. If a total prosthesis is implanted, theprosthesis head 104 is plugged on, and the replacement socket 106 isimplanted in the natural, optionally correspondingly prepared acetabulumas a counterpart to the prosthesis head 104. An articulation surface ofthe convex replacement-joint part 104 is provided for tribologicalpairing with an articulation surface of the replacement-joint part 106.

If a hemi-prosthesis is implanted, the prosthesis head 108 is plugged onas a counterpart to the natural acetabulum. An articulation surface ofthe convex replacement-joint part 108 is provided for tribologicalpairing with the natural joint surface (for example, cartilage) of thenatural acetabulum.

With the implant set 100, under some circumstances, it needs to bedecided intraoperatively whether a hemi-prosthesis or a total prosthesisis to be implanted. For example, if the cartilage of the natural,concave tribological surface of the acetabulum is healthy and intact, ahemi-prosthesis may be adequate. If the cartilage of the acetabulum isdamaged or unhealthy, a total prosthesis may be required.

As suggested in FIG. 1, the two replacement heads 104 and 106 can bedifferent in size. For example, an outer periphery of thehemi-prosthesis 108 can, in fact, correspond with an outer periphery ofthe hip-socket insert 106, that is, the total prosthesis head 104 has asmaller circumference than the hemi-prosthesis head 108 because of itsinterplay with the total prosthesis socket 106.

The two prosthesis heads 104 and 108 can also differ in the materialsused. Even if a base body of both heads 104, 108 is made from the samemetal or the same ceramic, the articulation surfaces can differ. Inparticular, an articulation surface of the implant 108 can be coated ina cartilage-friendly manner with regard to a tribological pairing with anatural joint surface, while such a coating is not necessary for thereplacement head 104. With different exemplary embodiments, for example,the running surface of the head 104 may not be further coated for thetribological pairing with the socket 106, or may be coated, for example,with a material such as polyethylene, while an articulation surface ofthe head 108 may be coated with PCU. This coating must be attachedpermanently and securely to the base body of the head 108, wherein sucha base body transfers forces occurring in the hip joint and alsoestablishes the connection to the shaft system of the prosthesis forthis purpose.

FIG. 2 shows a semi-transparent schematic view of the hemi-prosthesishead 108 from FIG. 1. A solid base body 202 comprises, for example, ametallic material such as stainless steel. The coupling element 116 inthe form of a conical plug is suggested.

A surface of the base body 202 forms a substrate 204 for the actualarticulation surface 206. This is provided by a coating 208 of PCUpresent on the substrate 204. In the hardened condition, the coating 208in the example from FIG. 2 forms a casing or respectively a cap 209 onthe base body 202, which may be metal. The cap 209 extends down to apedestal 210 at the bottom of the base body 202. The pedestal 210 can beleft free, since the articulation surface 206 for the tribologicalpairing with a natural acetabulum does not extend down to the pedestal210. If the pedestal 210 can enter into an interaction with theprosthesis shaft 102 (FIG. 1), it may be advantageous to leave thepedestal free, if the interaction partners are made from the samematerial or material of the same hardness. By way of difference fromFIG. 1, with other exemplary embodiments, a coating material can alsocompletely cover a base body, for example, because of a generally betterbiocompatibility of the coating by comparison with the material of abase body.

The substrate 204 embodies a plurality of raised structures, namelyteeth 212. The teeth 212 can be formed, for example, in one piece withthe base body 202, or the teeth 212 can be manufactured separately (forexample, in the form of rows of teeth) and, for example, introduced insuch a manner into the base body 202 that they extend outwards throughopenings in the base surface or respectively the substrate 204. Theteeth 212 are arranged in a plurality of rows 214, which extend in eachcase between a top 216 of the head and a bottom 218 or the pedestal 210and are arranged at regular intervals around the periphery of the head108. In this manner, the teeth 212 form a relief 220, which coversuniformly a large part of the substrate 204, wherein a region close tothe top 216 and a region close to the bottom 218 can be excluded.

As is evident, for example, with regard to the row of teeth 222illustrated in profile, the rows of teeth 214 engage in the coating 208.Accordingly, the less rigid cap 209, by comparison with the base body202, is disposed not merely on a flat substrate of the more rigid basebody 202, but the rows of teeth 214 allow a comparatively improvedadhesion of the PCU cap 209 on the steel body 202. The rows of teeth 214minimize tangential displacements of the cap 209 both in thelongitudinal direction (arrow 224) and also in a transverse direction(arrow 226) perpendicular to the latter, and accordingly, also incombinations of such directions.

The PCU material of the cap 209 is less rigid by comparison with theforce-transmitting base body 202; that is, the PCU material of the cap209 is insufficiently rigid for a permanent transmission of forcesacting in the hip joint. However, in order to achieve reliablerestriction of the movement of the cap 209, not only one tooth or a fewteeth are provided, but the two-dimensional relief 220 is embodied witha plurality of teeth 212 or respectively rows of teeth 214.

On the one hand, stresses within the cap 209, which could lead, forexample, to the formation of cracks, can be minimized as a result. Onthe other hand, each individual tooth 212 or each individual row ofteeth 214 must absorb only a small part of the force acting tangentiallyto the substrate 204, so that a loosening, wearing out etc. of therelatively soft material of the cap 209 around a tooth 212 or row ofteeth 214 can be minimized, and accordingly, consequences, such as anincreased mobility of the cap, a formation of cracks at the positions ofthe teeth 214, etc. can be avoided. Too few teeth and/or excessivelypronounced teeth can lead to a piercing, tearing or other localover-stressing of the cap material.

In this manner, the relief 220 can contribute to a permanent andreliable attachment of the cap 209 to the base body 202. With differentexemplary embodiments, for example, rows of teeth in the transversedirection, crossing rows of teeth, etc. can also be provided alongsiderows of teeth in the longitudinal direction. Corresponding reliefs canbe embodied, for example, dependent upon the coating material and/orbase-body material used, the type of joint or respectively anticipatedstresses on the replacement joint, anticipated joint movements andintensities of movement and so on.

Additionally or alternatively to teeth or respectively rows of teeth,other relief-like structures may be present. For example, the relief 220could be supplemented in two-dimensional regions 228 between the rows ofteeth 214 through roughening or ribbing in order to further improve anadhesion of the cap 209. However, reliefs formed from only onestructural element, such as teeth, may be more cost favorable tomanufacture. Instead of or in addition to teeth, for example, spikes ofconical or cylindrical shape or barbs with two edges can be provided.Teeth could be provided, for example, with different polyhedral shapes,for example, with three, four or more edges.

The shape and the depth of individual structural elements can also beadapted to the circumstances of the intended application. On the onehand, the teeth 212 should be sufficiently large to guarantee anadhesion of the cap 209, but not so large that there is a risk ofpiercing of the coating 208. A maximum projection of the teeth 212 abovea base level of the substrate 204, as defined by a tooth-free region ofthe substrate 204 may therefore be a fraction of the thickness of thecoating 208, for example, the teeth can have a maximum height of 70% orless, 50% or less, or 30% or less of the thickness of the coating 208.

Teeth of different size and/or depth can be used in one and the samerelief. For example, teeth close to the top and/or the bottom of areplacement ball-joint head can be formed smaller than in a centralregion.

Other exemplary embodiments of implant sets, for example, for hipprostheses, are not embodied in a modular manner but contain a totalprosthesis embodied in one piece as a femur shaft with head, forexample, a mono-block femur shaft with joint head, and, in addition, atleast one replacement hip socket, and a hemi-prosthesis embodied in onepiece as a femur shaft with head, for example, also a mono-block femurshaft with a joint head. Optionally, individual components or all ofthese components are present in different sizes. The properties of thehemi-prosthesis in the head region can correspond to those describedabove for the modular head system 108, apart from the fact that thecoupling 218 is dispensed with.

FIG. 3 shows in schematic form components of an implant set 300 for areplacement shoulder joint. The implant set 300 comprises an implantbase, namely a short humerus shaft 302, and a convex total prosthesispart, namely a total prosthesis head 304, as a total prosthesis implant,with which a concave total prosthesis part not illustrated here, namelya total prosthesis shoulder socket, is associated as a replacementshoulder socket/glenoid. The implant set 300 further comprises a convexhemi-prosthesis part, namely a hemi-prosthesis humerus head 306 as ahemi-prosthesis implant. The implant set 300 can comprise more than thecomponents shown, for example, the shaft, prosthesis heads and/orprosthesis sockets can be provided in different sizes, made fromdifferent materials and so on.

The short humerus shaft 302 is provided for anchoring in the humerusbone by means of an anchor region 308 with bone fenestration. For theimplantation of a total prosthesis, inter alia, a humerus joint head isreplaced by the total prosthesis head 304. For the implantation of ahemi-prosthesis, the humerus joint head is replaced by thehemi-prosthesis head 306.

The humerus shaft 302 can comprise, for example, a metal, such astitanium, a titanium alloy, etc. Optionally, a coating can be provided,for example, on the anchor 308, which promotes a secure anchoring in thebone through bone growth. For the holding of precisely one of theprosthesis heads 304 or 306, the shaft 302 comprises a holding portion310, which provides, for example, a plug-in shaft for the plug-inconnection of one of the heads 304 or 306. If a total prosthesis isimplanted, the prosthesis head 304 is plugged onto the shaft and aglenoid replacement-joint part is implanted as a counterpart. If ahemi-prosthesis is implanted, the prosthesis head 306 is plugged in as acounterpart to the natural glenoid.

With the implant set 100, under some circumstances, it needs to bedecided intraoperatively whether a hemi-prosthesis or a total prosthesisis to be placed. For example, if the cartilage of the natural, concavetribological surface of the glenoid is healthy and intact, ahemi-prosthesis may be sufficient. If the glenoid cartilage is damagedor unhealthy, a total prosthesis may be required.

Accordingly, an articulation surface of the replacement-joint part 304is adapted to a tribological pairing with an articulation surface of theglenoid replacement-joint part. An articulation surface of the convexreplacement-joint part 306 is provided for a tribological pairing withthe natural joint surface (for example, cartilage) of the naturalglenoid.

The two prosthesis heads 304, 306 can differ in constituents ormaterials, with regard to the presence and composition of coatings, etc.Even if the base body of both heads 304 and 306 is made from the samebasic material, such as a metal or ceramic, the articulation surfacescan be formed from different materials. In one exemplary embodiment, therunning surface of the implant 304 has no further coating, while thearticulation surface of the head 306 is formed by a coating. The coatingof the head 306 can comprise, for example, PCU and should be attached inan inseparable manner to the base body of the head 306 which bears theload and makes the connection to the shaft system 302 of the prosthesis.

FIG. 4 is a semi-transparent schematic presentation of thehemi-prosthesis head 306 from FIG. 3. A solid base body 402 comprises,for example, a ceramic material. The coupling element 404 in the form ofa plug-in cone serves for the coupling with the shaft 302.

A surface of the base body 402 forms a substrate 406 for the actualarticulation surface 408. The latter is provided by a coating 410 madeof PCU present on the substrate 406. In the example of FIG. 4, in thehardened condition, the coating 410 forms a casing or a cap 411 on theceramic body 402. The cap 411 can completely cover an upper side orouter surface of the body 402 and can engage under an underside of thehead 306, on which the coupling 404 is disposed. In particular, the cap411 can extend down to a back-cut pedestal 412.

The substrate 406 embodies a plurality of grooves 414 (anchoringgrooves). On the one hand, longitudinal grooves 416 are provided, whichextend between a top 418 of the head and a base 420 respectively thepedestal 412 and are arranged at regular intervals around the peripheryof the head 306. Furthermore, transverse grooves 422 are provided, whichextend along from the peripheral lines approximately in a region closeto the base 420.

Longer longitudinal grooves 426 and shorter longitudinal grooves 424 areprovided. The transverse grooves 422 do not extend around the entirehead 306 but are interrupted or respectively extend between thelongitudinal grooves 426. In this manner, the grooves 414 form a relief428 which covers the substrate 406. The relief 428 is more or lesspronounced in different locations, since the transverse grooves 414 arepreferably present close to the substrate 420.

The cap 411 formed by the coating 410 is disposed not only on thesubstrate 406 but engages in the groove 414 of the base body 402.Accordingly, the cap 411, which is less rigid by comparison with thebase body 402, is disposed not only on a locally flat substrate of therelatively more rigid base body 402, but the grooves 414 allow animproved adhesion of the PCU cap 411 on the ceramic body 402 bycomparison. The longitudinal grooves 416 minimize transversedisplacements of the cap 411, and the transverse grooves 422 minimizelongitudinal displacements of the cap 411 and thus improve the holdingof the cap 411.

The PCU material of the cap 411 is less rigid or respectively softer andmore flexible by comparison with the force-transmitting base body 402.However, in order to achieve a reliable restriction of the movement ofthe cap 411, it is advantageous to provide not only one singlelongitudinal groove and/or a single transverse groove (or a few punctualindentations) in the substrate 406, but rather a two-dimensional relief,as suggested by way of example with the relief 428 in FIG. 4.

On the one hand, stresses within the cap 411, which could lead to theformation of cracks as a result of movements of parts of the cap 411against one another, can be minimized by the relief 428. On the otherhand, each individual rib (or respectively edge, comb) of the coating410 which engages in a groove 414, must take up only a small part of aforce acting tangentially to the substrate 406, so that a loosening orwearing out of the material of the cap 411 in the region of the groovescan be minimized. Too few and/or excessively pronounced grooves can leadto local differences in the rigidity of the coating 410 and consequentlyto the formation of cracks or other local over-stressing of the cap.

In this manner, the relief 428 can contribute to a permanent andreliable attachment of the cap 411 on the base body 402. Additionally oras an alternative to grooves, other relief-like structures can also bepresent. For example, the relief 428 could be supplemented by roughened,two-dimensional regions 430 between the grooves 414, in order further toimprove an adhesion of the cap 411.

The grooves 414 should be deep enough to guarantee an adhesion of thecap 411. A maximum depth of the grooves below a base level of thesubstrate 406, as defined locally, for example, by a groove-free regionof the substrate 406, can therefore constitute a fraction of thethickness of the coating 410. For example, the grooves can have amaximum depth of approximately 70% or less, 50% or less, or 30% or lessthan the thickness of the coating 410.

A profile of the grooves can be embodied dependent upon the material ofthe substrate 406, the coating 410 and/or other circumstances in theindividual case. For example, the grooves can be provided in triangular,rectangular, trough-like and/or other shapes. The depth, profile and/ornumber of the grooves can also be varied. For example, by comparisonwith a given configuration, a larger number of grooves can be provided,which are, however, flatter in order to achieve a specified adhesioneffect. If very many mutually crossing grooves are provided, a reliefwith ribbing is achieved, as will be discussed by way of example below.

With some exemplary embodiments, more transverse grooves can be providedthan suggested in FIG. 4; the additional transverse grooves couldextend, for example, closer to a top of the base body. With otherexemplary embodiments, more longitudinal grooves could be provided. Thetransverse grooves 414 in FIG. 4 are provided with interruptions at thepositions of the longitudinal grooves 426. Interruptions could also beprovided in the longitudinal grooves. Instead of providing onlylongitudinal grooves and/or transverse grooves, grooves with otherorientations could also be provided additionally or alternatively, forexample, diagonal grooves. Grooves could also cross one another withoutinterruptions. A relief with crossing grooves is described below.

Other exemplary embodiments of an implant set for shoulder prosthesesare not embodied in a modular manner but contain a total prosthesisembodied in one piece as a humerus shaft with a head, for example, amono-block shoulder-shaft system with humerus head, and, in addition, atleast one glenoid replacement, and a hemi-prosthesis embodied in onepiece as a humerus shaft with a head, for example, also a mono-blockshoulder-shaft system with a humerus head. Optionally, individualcomponents or all of these components may be present in different sizes.The properties of the hemi-prosthesis in the head region can correspondto those which were described above for the modular-system head 306,apart from the fact that the coupling 404 is absent.

FIG. 5 shows in a schematic semi-transparent partial view, an implant500 for use as a femur or respectively condyle joint replacement in theform of a hemi-prosthesis. The implant 500 can be, for example, a partof an implant set for knee prostheses, wherein the set could alsocomprise, for example, a total prosthesis alongside the hemi-prosthesis500.

The implant 500 comprises a base body 501 with a condyle replacement orrespectively a joint knuckle 502. The condyle 502 can be solid and canbe embodied, for example, in stainless steel. In the following, the basebody 501 and joint condyle 502 are occasionally equated. A surface ofthe condyle 502 forms a substrate 504 for a cartilage-friendly coating506, which can comprise, for example, PCU. The coating 506 forms anarticulation surface 508 for articulation with a joint surface of anatural femur.

The coating 506 forms a casing or respectively a cap 510 on the condyle502, wherein the cap 510 completely covers an outer surface of thecondyle 502. With other embodiments, the coating 506 can also coverfurther surface regions 512 of the base body 501.

The substrate 504 is formed by a roughened surface which is suggested inFIG. 5 by an irregular contour line 514 and hatching 516 and, in thisexample, covers the entire condyle 502. Accordingly, the cap 510 is notdisposed on a locally flat substrate, but is disposed in engagement withthe roughened surface of the body 502, so that an improved adhesion ofthe cap 510 on the condyle 502 is guaranteed in this manner.

The rough substrate 504 minimizes displacements of the cap 510 resultingfrom the effects of tangential forces relative to the substrate 504. Theroughening 514, 516 is a further example 518 for a two-dimensionalrelief which is appropriate for absorbing and transferring tangentialforces locally in different regions of the articulation surface 508,and, in this manner, minimizing, on the one hand, undesirable movementsor displacements of the cap 510 and, on the other hand, minimizing theoccurrence of cracks or other damage to the coating 506.

By contrast with the image in FIG. 5, only partial regions of a condyle,a head or another component may be roughened for the tribologicalpairing. The indentations and raised areas of the relief 518 orrespectively of the roughening 514, 516 should be sufficientlypronounced in order to guarantee an improved adhesion of the cap 510 bycomparison with a flat substrate. The maximal raised areas orrespectively indentations can range within the order of magnitude offractions of a thickness of the coating and can be, for example, 70% orless, 50% or less, or 30% or less of a thickness of the coating 506.

FIG. 6A shows schematically a plan view of the detail of a relief 600,as could be stamped into or onto or on a substrate of thehemi-prosthesis implant in order to optimize an adhesion for a coatingfor the embodiment of an articulation surface. In the exemplaryembodiment of FIG. 4, the relief 428 comprises a plurality of grooves414 embodied without crossings. In the exemplary embodiment of FIG. 6A,by contrast, the relief 600 comprises a plurality of mutually crossinggrooves 602. In the case of parallel grooves 604, for example, thesecould be longitudinal grooves, and in the case of parallel grooves 606,these could be transverse grooves. However, the grooves 604, 606 canalso run in other directions, for example, in diagonal directionsrelative to a top or a bottom, for example, of a convexreplacement-joint part, wherein the direction towards the top orrespectively bottom is indicated by arrows 608 or respectively 610.

For the embodiment of the grooves 602, the same applies as discussed forthe grooves 412 of FIG. 4. The grooves 602 define raised regions 612, ofwhich the edges 614 lead to a restriction of movement in the event oftangential forces acting on an attached coating and accordingly animproved adhesion of the coating on the substrate. As shown by theexample in FIG. 6A, the relief 600 can be described, on the one hand, asa patterning determined by the grooves 602, wherein the grooves 602 areindentations relative to a base surface or respectively an imagined flatsubstrate. However, this description is arbitrary because, on the otherhand, the relief 600 can also be described as a pattern of raisedregions 612. Which form of description is selected can be madedependent, for example, upon manufacturing, for example, if the relief600 is generated by the introduction of grooves 602. However, otherapproaches are also conceivable.

FIG. 6B shows schematically a detail in plan view of a further exemplaryembodiment of a relief 620. The latter comprises a ribbing 621 for theimprovement of an adhesion of the coating. The ribbing 621 comprises aplurality of grooves, channels or corrugations 622 which define aplurality of raised regions 624. Each of these regions forms a tooth626. Each tooth has four edges or ridges 628 and a tip 630. Otherdesigns, for example, other polyhedral shapes with fewer or more edgesare also conceivable.

FIG. 6C shows a schematic cross-section through a substrate 642 which isformed by a surface of a base body 644, and in which a plurality ofraised regions 648 are embodied for the improved adhesion of a coating646. The raised regions 648 each provide two hook-like structures 650 ina region facing towards the coating 646. The hooks 650 can be embodiedon both sides as shown, or also only on one side.

According to a complementary description of the configuration of FIG.6C, grooves, channels or indentations 652 are introduced into thesubstrate 642, wherein the grooves 652 provide overhanging edges.Structures such as those shown in FIG. 6C could be introduced into ametallic base body, for example, by milling metal processing or into aceramic base body by means of ceramic casting.

FIG. 7A shows an exemplary embodiment of a base body 702 for ahemi-prosthesis head, wherein the coating or respectively cap or casinghave been omitted here. For a hemi-prosthesis head for which the basebody 702 could be used, the discussion with reference to the prosthesishead 108 of FIGS. 1 and 2 applies by analogy.

The base body 702 can be embodied from a metallic material, such assteel. A coupling element in the form of a conical plug 704 issuggested. A surface of the base body 702 forms a substrate 706 for acoating to be applied. The substrate 706 embodies a plurality of grooves708. Unless otherwise stated, the description discussed, for example,with reference to the grooves 414 of the exemplary embodiment of FIG. 4also applies for these grooves 708 by analogy.

FIG. 7B shows a cross-sectional profile through the base body 702 withthe grooves 710 along the line A-A in FIG. 7A. The groove 710 isintroduced into the base body 702 with lateral walls 712 and a base 714.The lateral walls 712 can be embodied as undercuts, that is, withoverhanging edges, as was described with reference to FIG. 6C. Aborehole 716 is introduced into the bottom 714 of the groove 712, whichcan extend continuously through to an internal region of the base body702. For example, the borehole 716 can open into the cone 704, which isshown in FIG. 7A.

During the course of manufacture of the hemi-prosthesis 700, thesubstrate 706 is coated with a synthetic material, for example, in aninjection molding process. In this context, the base body 702 can beused as a metallic insert component. During the course of injection overthe substrate 706 with the synthetic material, the borehole 716 servesfor ventilation. This can, for example, improve the adhesion of theresulting coating or respectively cap.

As indicated in FIG. 7B, an area of the substrate 706 occupied by aventilation borehole 716 can, in general, be considerably smaller thanan area occupied by an indentation, such as the groove 710 orrespectively its bottom 714. Ventilation boreholes, channels or openingscan be, for example, less than 50%, less than 30%, less than 20% or lessthan 10% of the bottom area of the groove or other indentation.

The ventilation borehole 716 leads perpendicularly away from thesubstrate 706 or respectively the base 714 of the groove 710 into theinterior of the base body 702, that is, at an angle of 90° to the localsurface 706, 714 of the base body 702. With other exemplary embodiments,the borehole can also extend diagonally, that is, with an angledifferent from 90°, that is, for example, with an angle of 80° or 70°.This can be advantageous, for example, so that a borehole can reach aninterior hollow cavity of the base body.

Furthermore, a ventilation groove 720 is indicated in FIG. 7B, which isintroduced into the substrate 702, and, in fact, starting from thegroove 710 and leading away from the latter. The groove 720 also servesfor the ventilation and therefore for the attainable improved adhesionof a coating applied to the substrate 706 or respectively to the basebody 702. The embodiments of the ventilation borehole 716 also apply byanalogy for the ventilation groove 720 where applicable.

Ventilation grooves can lead perpendicularly, that is, at an angle of90°, from a groove, such as the groove 710, or can lead away at adifferent angle, for example, 75° or 45°. Ventilation grooves can beshort, so that a length of the ventilation groove is, for example,shorter than or equal to the width or the depth of the indentation, forexample, a groove, to be ventilated. However, ventilation grooves canalso be long and can extend over a multiple of the width of anindentation to be ventilated. In the case of given exemplary embodiment,a ventilation groove can connect several structures to be ventilated toone another, such as several grooves, for example, the grooves 708 inFIG. 7A.

Several ventilation boreholes and/or grooves can be provided for eachstructure to be ventilated. For example, 3 ventilation grooves or 10ventilation grooves can be provided on each side of the groove 710 inFIG. 7A.

Ventilation boreholes, such as the borehole 716, can be arranged in anindentation, for example, of a groove, like the groove 710 in FIG. 7B,in grooves 602 in FIG. 6A, in channels 622 as in FIG. 6B and so on.Similarly, ventilation grooves can lead away from such indentations.

FIG. 7A shows that the coating substrate 706 is provided adjoining apedestal 730 of the base body 702 with a peripheral anchoring groove732.

FIG. 7C shows a further cross-sectional profile through the base body702, wherein the profile intersects the pedestal 730 and the anchoringgroove 732. The groove 732 can be provided dependent upon the coatingmaterial used, in order to optimize an anchoring of the coating orrespectively of the casing formed by the coating on the base body 702. Adepth 734 of the groove 732 and/or further design parameters can beestablished dependent upon the coating material, purpose of use, thatis, upon the type of prosthesis and the forces transmitted etc.

The groove 732 is shown in FIG. 7A as peripheral, however, modificationsare possible; for example, an anchoring groove may be embodied only inparts or segments. Instead of one complete or partial peripheralanchoring groove, several (transverse) anchoring grooves can be providedparallel to one another, wherein the transition to transverse grooves736 can extend in a flowing manner.

In principle, it is conceivable for an anchoring groove to be providedwith a spacing distance relative to a pedestal region of the base body;however, for the present, if an anchoring groove is regarded asexpedient, the configuration shown in FIGS. 7A and 7C, in which theanchoring groove 732 is provided directly on the pedestal 730, ispreferred. This minimizes a joint gap at the transition 738, which canoccur between the base body 702 and respectively the outer surface 740of the pedestal 730, on the one hand, and an applied coating, on theother hand, wherein, after the application, the coating forms a cap 742as indicated by the dashed line. The cap 742 can be formed, for example,from an injection molded PCU material.

In order to minimize a joint gap at the transition 738 from the PCUtribological surface 744 of the cap 742 to the metallic pedestalexterior 740 gap, the outer edge or corner 746 of the pedestal undercut748 of the pedestal 712 can be embodied with sharp edges, and thepedestal edge 748 can otherwise extend in a straight line withoutstructuring in the direction towards the substrate 706 or respectivelythe groove 732. In this manner, a flush mounting, for example, ofinjection-molded material on the pedestal edge 748 can be facilitated.If the edge 746 were to be embodied in a rounded manner, it can occurthat the injection molded material used does not wet up to the outeredge of the pedestal accurately. In such cases, an indentation or troughcould be formed, for example, at the transition between syntheticmaterial surface and metal surface.

FIG. 8 shows a view of a hemi-prosthesis head 800 which can be avariation of the prosthesis head 108 of FIG. 2; such aspects, in whichthe two heads 108 and 800 can be identical, will not be describedexplicitly again in the following.

A base body 802 offers a substrate 804 for a coating 806 or cap 807, onwhich or by which the articulation surface 808 is formed. Expressed moreaccurately, the cap 807 covers the base body 802, wherein the cap 807extends down to a pedestal 810 of the head 800. Without the pedestal810, the head 802 has an approximately spherical shape, so that asurface of the cap 807 also assumes a spherical shape.

FIG. 8 indicates an equator 812, wherein the term “equator” relates tothe approximately spherical shape of the cap 807, as is known to theperson skilled in the art. The surface of the cap 807 in a region 814above the equator 812 represents the actual articulation surface 808,that is, in the case of normal joint movements, the region 814 providesthe articulating zone or respectively the articulation regioninteracting with the (natural) joint counterpart. Under normal movementconditions, a region 816 below the equator 812 does not belong to thearticulating zone 808.

The substrate 804 embodies a plurality of teeth 818, as was described indetail for the exemplary embodiment of FIG. 2 with teeth 212. In theexample in FIG. 8, the teeth 818 are also arranged in a plurality ofrows of teeth 820. However, by way of difference from the exemplaryembodiment of FIG. 2, the rows of teeth 820 are provided only outsidethe normal articulation zone 814, that is, in the region 816 adjoiningthe pedestal 810, while, in the region 814, that is, below thearticulation zone 808, the substrate 804 is free from teeth or otherrelief structures, that is, the substrate 804 is flat below thearticulation surface 808.

An adhesion or respectively anchoring effect of the cap 807 on the basebody 802 achieved with the rows of teeth 820 can be sufficient so that arelief below the articulation surface is not required. Conversely, if anabsence of a relief below the articulation zone 808 is required, forexample, for safety reasons, an adequate adhesive affect can still beachieved, as shown by the example of FIG. 8. Optional additionalmeasures to be taken, for example, the provision of ventilationboreholes or grooves to facilitate the expulsion of air during aninjection molding of the coating 806, thereby achieving an improvedadhesive effect, have not been shown in the drawing.

The humerus head 306 from FIG. 4 could also be modified in such a mannerthat the grooves 414 below the articulation surface 408 can be omittedin their entirety or in part. For example, a relief could be providedoutside the articulation surface 408 in a region 432 (compare FIG. 4).The area 432 faces towards the (remaining, resected) humerus and extendsdown to the backwardly offset pedestal 412, which adjoins the prosthesisshaft 310, (compare FIG. 2). The area 432 provides the substrate for thecap 411 in a region in which the cap 411 engages around the outer edge434 of the base body 402, which limits the articulation surface 408.

For example, longitudinal grooves and/or transverse grooves can beprovided in the region 432 (not visible in FIG. 4), for which the samedescription applies by analogy with regard to their embodiment,extension etc., as was described explicitly for the grooves 414, 416,422 shown in FIG. 4. For an improvement of the adhesive effect, it isalso conceivable to provide ventilation boreholes and/or grooves, and,in fact, either in the articulation region 408, even if a relief has notbeen provided there, or in the region 432, or in both regions 408 and432.

FIG. 9 shows a flow chart with an exemplary embodiment of a method 900for the manufacture of a hemi-prosthesis implant. In step 902, a reliefis provided on a substrate of a replacement-joint part for the improvedadhesion of a coating to be applied downstream. The relief can beprovided, for example, during the manufacture of a base body of thereplacement part. Accordingly, a relief structure can be embodied, forexample, on or in a metallic or ceramic body by means of casting,modelling, stamping, pressing etc. Additionally or alternatively, adownstream processing can be implemented after a manufacture of a basebody. For example, using chip-removing or milling processes, grooves canbe introduced into a metallic body as shown in FIG. 4 or 6A. A roughenedsubstrate, as suggested in FIG. 5, can be introduced into a metallicbody using a blasting process.

In step 904, the coating is applied to the substrate which has beenprepared, that is, provided with a relief. For example, a syntheticmaterial such as a TPE, for example, PCU, can be applied to thesubstrate by means of injection molding. The material flows around therelief structures. After a hardening, the coating encloses raised reliefstructures or respectively fills indented relief structures.Accordingly, the coating adheres to the base body in a special manner.

In step 906, the method 900 is completed, for example, by integratingthe manufactured hemi-prosthesis implant in an implant set. Methods suchas the method 900 and modifications thereof allow a cost-favorablemanufacture of coatings for strong joint replacement hemi-prostheseswith biocompatible articulation surface.

The invention is not restricted to the exemplary embodiments describedhere and the aspects emphasized here. On the contrary, especially butnot exclusively within the field indicated by the appended claims, aplurality of modifications is possible, which are disposed within thescope of activities of a person skilled in the art. In particular, givencombinations of features described separately above will be evident tothe person skilled in the art as expedient or advantageous.

The invention claimed is:
 1. A hemi-prosthesis implant comprising: areplacement joint part with an articulation surface for tribologicalpairing with a joint surface of a natural joint counterpart, wherein thearticulation surface is embodied with a coating applied to a substrate,wherein the substrate provides a relief for adhesion of the coating, andwherein in an indentation of the relief one or more of a ventilationborehole located at the lowest part of the bottom of the indentation andleading into the substrate and a ventilation groove starting at the topedge of the indentation and leading away from the indentation ispresent.
 2. A hemi-prosthesis implant according to claim 1, wherein therelief provides a plurality of grooves.
 3. A hemi-prosthesis implantaccording to claim 2, wherein the relief provides a plurality oflongitudinal grooves and transverse grooves.
 4. A hemi-prosthesisimplant according to claim 1, wherein the relief provides a ribbing. 5.A hemi-prosthesis implant according to claim 1, wherein the reliefcomprises at least one roughened substrate region.
 6. A hemi-prosthesisimplant according to claim 1, wherein the substrate is formed from oneor more of a metal, a ceramic, and a reinforced synthetic material.
 7. Ahemi-prosthesis implant according to claim 1, wherein a material of thecoating comprises one or more of a thermoplastic elastomer,polycarbonate urethane, a polyolefin polymer, a polyaryl ketone, and ahydrogel.
 8. A hemi-prosthesis implant according to claim 1, wherein anat least partially peripheral anchoring groove is embodied directly onan outer pedestal of a base body forming the substrate.
 9. Ahemi-prosthesis implant according to claim 1, wherein the relief isembodied entirely or partially outside the articulation surface.
 10. Ahemi-prosthesis implant according to claim 1, wherein the implantcomprises a humerus-head hemi-prosthesis, a femur-head hemi-prosthesis,a hemi-prosthesis femur component, or a talar-body hemi-prosthesis. 11.A hemi-prosthesis implant according to claim 1, wherein in theindentation of the relief the ventilation borehole located at the lowestpart of the bottom of the indentation and leading into the substrate andthe ventilation groove starting at the top edge of the indentation andleading away from the indentation are present.
 12. A hemi-prosthesisimplant according to claim 11, further comprising a metallic base body,wherein the substrate is on a surface of the metallic base body, andwherein the borehole located at the lowest part of the bottom of theindentation extends continuously from the indentation through themetallic base body to an internal region of the metallic base body. 13.An implant set comprising: an implant base for holding a replacementjoint part; a total prosthesis implant with a first replacement jointpart with an articulation surface for tribological pairing with anarticulation surface of a second replacement joint part of the totalprosthesis implant; and a hemi-prosthesis implant with a thirdreplacement joint part, the third replacement joint part having a thirdreplacement joint part articulation surface for tribological pairingwith a joint surface of a natural joint counterpart, wherein the thirdreplacement joint part articulation surface is embodied with a coatingapplied to a substrate, and wherein the substrate provides a relief foradhesion of the coating; wherein both the first and also the thirdreplacement joint part are embodied for holding by the implant base, sothat either a total prosthesis or hemi-prosthesis can be implanted, andwherein in an indentation of the relief one or more of a ventilationborehole located at the lowest part of the bottom of the indentation andleading into the substrate and a ventilation groove starting at the topedge of the indentation and leading away from the indentation ispresent.
 14. An implant set according to claim 13, further comprising ametallic base body, wherein in the indentation of the relief theventilation borehole located at the lowest part of the bottom of theindentation and leading into the substrate and the ventilation groovestarting at the top edge of the indentation and leading away from theindentation are present, wherein the substrate is on a surface of themetallic base body, and wherein the borehole located at the lowest partof the bottom of the indentation extends continuously from theindentation through the metallic base body to an internal region of themetallic base body.
 15. A method for manufacturing a hemi-prosthesisimplant, the method comprising: generating a relief on a substrate of areplacement joint part for adhesion of a coating; and injection moldingof the coating for embodiment of an articulation surface of thereplacement joint part for tribological pairing with a joint surface ofa natural joint counterpart; and disposing in an indentation of therelief one or more of a ventilation borehole located at the lowest partof the bottom of the indentation and leading into the substrate and aventilation groove starting at the top edge of the indentation andleading away from the indentation.
 16. A method according to claim 15,wherein the relief comprises one or more of a plurality of grooves, aplurality of teeth, a ribbing, and a roughened surface.
 17. A methodaccording to claim 15, wherein substrate is formed from one or more of ametal, a ceramic, and a reinforced synthetic material.
 18. A methodaccording to claim 15, wherein a material of the coating comprises oneor more of a thermoplastic elastomer, polycarbonate urethane, apolyolefin polymer, a polyaryl ketone, and a hydrogel.
 19. A methodaccording to claim 15, wherein the hemi-prosthesis implant comprises ahumerus-head hemi-prosthesis, a femur-head hemi-prosthesis, ahemi-prosthesis femur component, or a talar-body hemi-prosthesis.
 20. Amethod according to claim 15, further comprising: disposing in theindentation of the relief the ventilation borehole located at the lowestpart of the bottom of the indentation and leading into the substrate andthe ventilation groove starting at the top edge of the indentation andleading away from the indentation; forming the substrate on a surface ofthe metallic base body; and extending the borehole located at the lowestpart of the bottom of the indentation continuously from the indentationthrough the metallic base body to an internal region of the metallicbase body.